Laundry appliance

ABSTRACT

A laundry appliance ( 100;200 ) comprises an outer housing ( 102;202 ) and a drum ( 122;222 ) rotatably mounted therein. The drum ( 122;222 ) comprises an inner wall ( 32;132;232,232   a ) and an outer wall ( 34;134;234,234   a ), the inner and outer walls ( 32,34;132,134;232,234;232   a   ,234   a ) being perforated to allow washing liquid to flow into and out of the drum ( 122;222 ) via the perforations ( 42,44;42   a   ,44   a   ;42   b   ,44   b   ;42   c   ,44   c   ;42   d   ,44   d   ;42   e   ,44   e ). According to the invention, the area of the perforations ( 44;44   a   ;44   b   ;44   c   ;44   d   ;44   e ) per unit area of the outer wall ( 34;134;234,234   a ) is greater than the area of the perforations ( 42;42   a   ;42   b   ;42   c   ;42   d   ;42   e ) per unit area of the inner wall ( 32;132;232,232   a ).

[0001] The invention relates to a laundry appliance. Particularly, butnot exclusively, the invention relates to a washing machine.

[0002] A washing machine generally consists of an outer casing in whichis mounted a water-tight interior container or tub. A perforated drum iscommonly mounted inside the tub in a manner which allows the drum torotate with respect to the tub. During operation, washing liquid iscontained within the tub and the laundry to be washed is located withinthe perforated drum. The laundry is agitated, either by slow rotation ofthe drum or by the operation of an agitator located within the drum.When the laundry has been washed, some washing liquid is drained fromthe tub and further washing liquid is extracted from the laundry byspinning of the drum within the interior container to spin washingliquid therefrom. The extracted water exits the drum through theperforations in the wall thereof. Extraction of rinse water is achievedin a similar manner.

[0003] It is understood that more water can be extracted from thelaundry if the drum is spun at higher spin speeds. There is thus atendency to spin the drum at as high a spin speed as possible.Increasing the spin speed, however, results in the need for a strongerdrum. One way to achieve this is to manufacture the drum with an innerwall and an outer wall. A drum having this type of configuration isillustrated in WO 99/58753. There is a risk, however, that water whichis being spun out of the drum during the spinning stage of a washingcycle will be retained between the inner and outer walls of the drum.This would add to the effective weight of the drum and result inexcessive consumption of energy.

[0004] It is an object of the present invention to provide a laundryappliance in which the drum is arranged so as to have adequate strengthto withstand the stresses imposed on it at high spin speeds and also toallow the egress of water or washing liquid from the interior of thedrum through the perforated walls in a manner which discourages waterretention between the inner and outer walls. It is a further object ofthe present invention to provide a laundry appliance in which the drumhas an outer wall and an inner wall and water egress therethrough is atleast as rapid as it would be through a drum having only a single wall.

[0005] The invention provides a laundry appliance comprising an outerhousing and a drum mounted rotatably therein, the drum comprising aninner wall and an outer wall, the inner and outer walls being perforatedto allow washing liquid to flow into and out of the drum via theperforations, characterised in that the area of the perforations perunit area of the outer wall is greater than the area of the perforationsper unit area of the inner wall.

[0006] The provision of two separate walls of the drum maintains thestrength thereof. The provision of perforations in the outer wall havingan area per unit area of the outer wall greater than the correspondingarea of the perforations in the inner wall reduces the risk of waterbeing retained within the space between the inner and outer walls.

[0007] Preferably, the total area of the perforations in the outer wallper unit area thereof is at least 10% bigger than the total area of theperforations in the inner wall per unit area thereof. More preferably,the total area of the perforations in the outer wall per unit areathereof is at least 20% bigger than the total area of the perforationsin the inner wall per unit area thereof. The comparatively large area ofthe perforations in the outer wall is useful in preventing waterbuild-up in the space between the inner and outer walls.

[0008] Further and advantageous features are set out in the subsidiaryclaims.

[0009] Embodiments of the invention will now be described with referenceto the accompanying drawings, in which:

[0010]FIG. 1 is a schematic sectional side view of a laundry applianceaccording to the invention;

[0011]FIG. 2 is a schematic sectional side view of an alternativeembodiment of the laundry appliance shown in FIG. 1;

[0012]FIG. 3 is a sectional view, shown on a greatly enlarged scale, ofa portion of a drum forming part of the washing machine shown in eitherof FIGS. 1 and 2;

[0013]FIG. 4 is a plan view of the wall portion shown in FIG. 3 showingthe hole configuration thereof;

[0014]FIG. 5 is a plan view, similar to FIG. 4, of an alternative wallportion having a first alternative hole configuration; and

[0015] FIGS. 6 to 9 are further plan views, similar to FIGS. 4 and 5, offurther alternative wall portions having second, third, fourth and fifthalternative hole configurations.

[0016] A laundry appliance in the form of a washing machine 100 is shownin schematic sectional side view in FIG. 1. The washing machine 100comprises an outer casing 102 which is supported on feet 104. Awater-tight tub 106 is mounted inside the outer casing 102 by means ofsprings 108 and dampers 110 in a known manner. In this way, the tub 106is able to move within certain limits with respect to the outer casing102. A water inlet 112 communicates with an upper portion of the tub 106and is connectable (by connection means not shown) to a suitable watersupply. A water outlet 114 communicates with the bottom of the tub 106and has a water pump 116 located therein so that water can be drainedfrom the tub 106 to a suitable drain. A door 118 is located in the frontof the outer casing 102 so as to provide access to the interior of thetub 106. A flexible seal 120 is provided between the tub 106 and thedoor 118 when the door 118 is in its closed position.

[0017] A drum 122 is rotatably mounted inside the tub 106. The drum 122is supported in cantilever fashion on a shaft 124 which, in turn, isrotatably supported on the tub 106 by bearings 126. A motor 128 isprovided inside the outer casing 102 and is connected in suitablefashion to the shaft 124 in order to effect rotation of the drum 122about its own longitudinal axis. The drum 122 has cylindrical walls 130which are perforated so as to allow water to pass through thecylindrical walls 130 of the drum 122.

[0018] The features of the washing machine described 100 thus far areknown. In operation, articles to be washed are introduced to theinterior of the drum 122 via the door 118. Thereafter, the door 118 isclosed. Water is then introduced to the tub 106 via the water inlet 112.Detergent is introduced to the interior of the tub 106 in any of avariety of known ways (e.g. via a soap tray, detergent ball or tablets).As the water level in the tub 106 rises, water enters the interior ofthe drum 122 via the perforations in the cylindrical walls 130 and wetsthe articles to be washed. A washing action is carried out by operationof the motor 128 which causes the drum 122 to rotate about its ownlongitudinal axis inside the tub 106. The speed of rotation is chosen sothat the wet articles are lifted out of the washing liquid andsubsequently dropped back thereinto. This known action effectivelyremoves dirt from the articles to be washed.

[0019] When the washing portion of the cycle is complete, the pump 116is operated so that water is drained from the lower part of the tub 106and passed to a drain via the water outlet 114. Washing liquid isfurther extracted from the wet laundry articles by increasing the speedof rotation of the drum 122 so that water is centrifugally extractedfrom the laundry articles and flung outwardly through the perforationsin the cylindrical walls 130. Water thus extracted drains to the lowerportion of the tub 106 and is then pumped away to the drain via thewater outlet 114. Rinse water is then introduced to the tub 106 via thewater inlet 112, a tumbling action is carried out so as to extractdetergent from the laundry articles and the rinse water is then drainedand spun out of the laundry articles as described above. This rinsingprocedure is commonly repeated at least three times.

[0020] The method outlined above is not new. Modifications to andvariations on the washing machine 100 and the method just describedabove are well known in the art and can be incorporated into the washingmachine 100 and its operation without departing from the scope of theinvention.

[0021] The present invention relates to the construction of the drum122, particularly to the construction of the cylindrical walls 130. Inorder to reduce the time required to dry articles which have been washedby an automatic washing machine, there is a general desire to increasethe speed at which the drum of the washing machine rotates or spins.Increasing the spin speed generally extracts more water from the laundryarticles and therefore drying can be achieved in a shorter time.However, increasing the spin speed necessitates some strengthening ofthe rotatable drum 122. In order to strengthen the drum 122, thecylindrical wall 130 consists of an inner wall 132 and an outer wall134, in contrast to a cylindrical wall having a single layer.

[0022] The inner wall 132 lies parallel to the outer wall 134 and, inthe embodiment shown in FIG. 1, the inner wall 132 extends across theentire depth of the drum 122. In an alternative embodiment, shown inFIG. 2, the drum arrangement is slightly different. Whilst all othercomponents shown in FIG. 2 remain identical to those illustrated in FIG.1, the drum 222 shown in FIG. 2, and its support means, are not.Specifically, the drum 222 comprises a first rotatable portion 222 a anda second rotatable portion 222 b. The first rotatable portion 222 a isrotatably supported in cantilever fashion, as before, by way of a firstshaft 224 a. The second rotatable portion 222 b is also supported incantilever fashion, this time on a second shaft 224 b, which isrotatably mounted inside the first shaft 224 a. The second rotatableportion 222 b is located inside the first rotatable portion 222 a at theend thereof adjacent the shafts 224 a,224 b. The motor 228 is arrangedso as to be able to drive the rotatable portions 222 a,222 b by way ofthe shafts 224 a,224 b so that relative rotation therebetween isachieved. The details and advantages of such an arrangement are set outand described in detail in WO99/58753.

[0023] The second rotatable portion 222 b extends across approximatelyone half of the depth of the drum 222. In the area in which the secondrotatable portion 222 b is provided (ie. the area adjacent the shafts224 a,224 b), the second rotatable portion 222 b forms an inner wall232. Radially outwardly of the second rotatable portion 222 b, lies partof the first rotatable portion 222 a. This part of the first rotatableportion 222 a forms an outer wall 234. Beyond the furthest extent of thesecond rotatable portion 222 b, the first rotatable portion 222 a has aconstruction similar to that shown in FIG. 1, i.e. the first rotatableportion 222 a has a cylindrical wall 230 comprising an inner wall 232 aand an outer wall 234 a.

[0024] As can be seen from the forgoing descriptions, most, if not all,of the cylindrical wall of the drum 122,222 comprises an inner wall132,232,232 a and an outer wall 134,234,234 a. In the embodiment shownin FIG. 1, the inner wall 132 and the outer wall 134 are fixedly joinedtogether so that the inner and outer walls 132,134 rotate together.Although the configuration of the embodiment shown in FIG. 2 allows thefirst and second rotatable portions 222 a,222 b to rotate independentlyof one another, the washing machine 200 will be configured and arrangedso that the first and second rotatable portions 222 a,222 b of the drum222 will be rotated at the same speed and in the same direction duringany spinning steps of the washing cycle. Thus, the first and secondrotatable portions 222 a,222 b will behave as a single unit during thewater extraction steps. In either embodiment, water extracted from thelaundry articles must therefore pass through both the inner wall132,232,232 a and the outer wall 134,234,234 a during spinning.

[0025]FIG. 3 shows, on a greatly enlarged scale, part of an inner wall32 and an outer wall 34 which could be used in either of the washingmachines 100,200 illustrated in FIGS. 1 and 2. Both walls 32,34 are madefrom metal (e.g. stainless steel) and have appropriate perforationsformed therein by either punching or stamping. The inner wall 32comprises an array of perforations 42 and the outer wall 34 comprises anarray of perforations 44. Arrow 46 indicates the direction of water flowduring a spinning step of the washing procedure.

[0026]FIG. 4 is a plan view, looking along the arrow 46, of the innerwall 32 shown in FIG. 3. The perforations 42 are shown in bold lineswith the perforations 44 formed in the outer wall 34 shown in dottedlines. As can be seen, the perforations 42 in the inner wall 32 form aregular array of holes having a 5 mm diameter and spaced 2 cm apart inhorizontal rows. The rows of perforations 42 are spaced 1.5 cm apart andalternate rows are offset by 1 cm with respect to the adjacent rows. Theperforations 44 located in the outer wall 34 are arranged in anidentical array but have a diameter of 10 mm. Thus, the total area ofthe perforations 44 in the outer wall 34 per unit area thereof is fourtimes larger than the total area of the perforations 32 in the innerwall 32 per unit area thereof.

[0027] An alternative arrangement is illustrated in FIG. 5. In FIG. 5,the array of perforations 42 a in the inner wall 32 is identical to thatof the perforations 42 shown in FIG. 4. The array of perforations 44 aformed in the outer wall 34 is similar to that of the perforations 44shown in FIG. 4, except that alternate perforations 44 a are omitted.Thus, a perforation 44 a is provided in respect of only alternateperforations 42 a. The total area of the perforations 44 a in the outerwall 34 per unit area thereof is thus only twice as large as the totalarea of the perforations 42 a in the inner wall 32 per unit areathereof.

[0028] In the arrangements shown in FIGS. 3, 4 and 5, each perforation44, 44 a in the outer wall 34 is radially aligned with a perforation42,42 a in the inner wall 32. By this we mean that, if a line were to bedrawn radially from the axis of rotation of the drum 122,222 through thecentre of any one of the perforations 44,44 a in the outer wall 34, thenit would have already passed through the centre of a perforation 42,42 ain the inner wall 32 by the time it reached the outer wall 34.

[0029] Radial alignment is, however, not essential to this invention.FIG. 6 shows a second alternative arrangement in which the array ofperforations 42 b in the inner wall 32 is the same as that shown inFIGS. 4 and 5. Again, the diameter of each perforation 42 b is 5 mm.However, the array of perforations 44 b arranged in the outer wall 34 isdifferent from either of those shown in FIGS. 4 and 5. In thisembodiment, the perforations 44 b are offset from the perforations 42 bin the inner wall 32 by 1 cm. Furthermore, the diameter of theperforations 44 b is 6 mm. This results in the total area of theperforations 44 b in the outer wall 34 per unit area thereof beingapproximately 40% greater than the total area of the perforations 42 bin the inner wall 32 per unit area thereof.

[0030] A further alternative configuration is illustrated in FIG. 7.Once again, the array of perforations 42 c formed in the inner wall 32is the same as that illustrated in FIGS. 4, 5 and 6. However, the arrayof perforations 44 c formed in the outer wall 34 is different. As in theembodiment illustrated in FIG. 6, the diameter of the perforations 44 cis 6 mm. However, there are fewer perforations 44 c formed in the outerwall 34 as illustrated in FIG. 7. In this arrangement, only threeperforations 44 c are provided for every four perforations 42 c. Thisarrangement gives a total area of the perforations 44 c in the outerwall 34 per unit area thereof of approximately 10% more than the totalarea of the perforations 42 c in the inner wall 32 per unit areathereof.

[0031] A third alternative embodiment is illustrated in FIG. 8. In thisembodiment, the array of perforations 42 d formed in the inner wall 32comprises rows of perforations 42 d of 3 mm diameter spaced aparthorizontally by a distance of 1 cm. Adjacent rows are spaced verticallyby a distance of 8.5 mm and offset by a distance of 5 mm. The array ofperforations 44 d formed in the outer wall 34 is made up of horizontalrows of perforations 44 d of 8 mm diameter and spaced apart by 2.5 cm.Adjacent rows, which are not offset, are spaced apart by 2.7 cm. In thisembodiment, the total area of the perforations 44 d in the outer wall 34per unit area thereof is approximately 5% greater than the total area ofthe perforations 42 d in the inner wall 32 per unit area thereof.

[0032] A fourth alternative embodiment is illustrated in FIG. 9. Thisembodiment is similar to that shown in FIG. 8 except that, in FIG. 9,the diameter of the perforations 44 e formed in the outer wall 34 is 11mm instead of 8 mm. This arrangement provides a total area of theperforations 44 e in the outer wall 34 per unit area thereof which isapproximately twice the total area of the perforations 42 e in the innerwall 32 per unit area thereof.

[0033] It will be appreciated that the structure and specific featuresof the washing machine 100,200 described above are mostly irrelevant tothe present invention. Therefore, alternative constructions of thesupport bearings, shafts, water inlet, water drain, door, etc andmethods of operation can be provided without departing from the scope ofthe invention. The invention relates simply to the construction of thecylindrical walls of the drum and features which do not relate to thisare regarded as inessential to the invention.

[0034] By providing an array of perforations in the outer wall of thedrum which has a total area of perforation per unit area of the saidwall which is greater than the area of the perforations provided in theinner wall per unit area thereof, it is perceived that the likelihood ofbuild up of water between the inner and outer walls during extractiontherethrough will be reduced.

1. A laundry appliance comprising an outer housing and a drum mountedrotatably therein, the drum comprising an inner wall and an outer wall,the inner and outer walls being perforated to allow washing liquid toflow into and out of the drum via the perforations, characterised inthat the area of the perforations per unit area of the outer wall isgreater than the area of the perforations per unit area of the innerwall.
 2. A laundry appliance as claimed in claim 1, wherein all of theperforations are circular.
 3. A laundry appliance as claimed in claim 1or 2, wherein the perforations in the inner wall are all the same size.4. A laundry appliance as claimed in any one of claims 1 to 3, whereinthe perforations in the outer wall are all the same size.
 5. A laundryappliance as claimed in claim 3 or 4, wherein each of the perforationsin the outer wall is larger than each of the perforations in the innerwall.
 6. A laundry appliance as claimed in claim 5, wherein the totalarea of the perforations in the outer wall per unit area thereof is atleast 10% bigger than the total area of the perforations in the innerwall per unit area thereof.
 7. A laundry appliance as claimed in claim6, wherein the total area of the perforations in the outer wall per unitarea thereof is at least 20% bigger than the total area of theperforations in the inner wall per unit area thereof.
 8. A laundryappliance as claimed in any one of the preceding claims, wherein eachperforation in the outer wall is radially aligned with one of theperforations in the inner wall.
 9. A laundry appliance as claimed in anyone of the preceding claims, wherein each of the perforations in theouter wall is larger than each of the perforations in the inner wall.10. A laundry appliance as claimed in any one of the preceding claims,wherein the perforations are formed by stamping or punching.
 11. Alaundry appliance as claimed in any one of the preceding claims, whereinthe inner wall is rigidly attached to the outer wall and is rotatabletherewith.
 12. A laundry appliance as claimed in any one of claims 1 to10, wherein the inner wall is rotatably mounted so as to be rotatableseparately from the outer wall.
 13. A laundry appliance as claimed inany one of the preceding claims, further comprising a watertight tub inwhich the drum is rotatably mounted, and the drum is rotatable about anaxis which is substantially horizontal.
 14. A laundry appliance asclaimed in any one of the preceding claims, wherein the laundryappliance is a washing machine.
 15. A laundry appliance substantially ashereinbefore described with reference to any one of the embodimentsshown in the accompanying drawings.